The three core domains that characterize autism are the domain of social behavior, the language domain and the restricted behavior domain (RB). RB consists of behaviors which represent distinct components of the larger construct (e.g. stereotyped, self-injurious, compulsive, ritualistic, sameness and restricted behaviors). This research will explore autism-specific neuroanatomic abnormalities and their relationship to RB using structural magnetic resonance imaging (MRI) shape and volume measures. Two main hypotheses drive this research. 1) There will be shape and volume differences between children and adolescents with autism and non-autistic children in brain regions previously related to RB, the caudate nucleus and the anterior cingulate gyrus. 2) Distinct Brain Regions measured using structural MRI, will be related to distinct components of RB. Specifically, A) Compulsive behavior will show a specific relationship to the anterior cingulate gyrus. B) Ritualistic behavior will show a specific relationship to the caudate nucleus. This research will inform our understanding of the biological basis of both repetitive behavior and autism, leading to better treatments and more directed genetic research.